That thing has to do with the brakes.
my kit included that too.... but i didnt use it cause i was just fine.... having ABS.
Aaahh ...... i don't really know the specific word to name it
but if ur car (like mine) has ABS unit, i think that u dont need it.
If you dont have ABS, u need it i think.
The work that this thing has to do, is to lower the position of the central brake unit.
Sorry for my english and hope u ll understand
anyone with a better explanation please???
have fun!!